Lawn mower

ABSTRACT

A lawn mower includes a drive source for driving a cutter blade, flaps, a grass clippings container, a grass clippings container weight detection unit, a travel distance detection unit, and a control unit. The control unit determines a change amount of weight of the grass clippings container detected by the grass clippings container weight detection unit over the elapsed time period from the time when detection of travel distance of the lawn mower is started by the travel distance detection unit to the time when travel of predetermined distance is completed, and implements control in a manner that the rotation speed of the drive source and the flap angle of the flaps are adjusted in accordance with the change amount of the weight.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2016-037050 filed on Feb. 29, 2016, thecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a technique of a rotary lawn mower forcutting lawn grass by a cutter blade accommodated in a housing.

Description of the Related Art

The rotary lawn mower cuts (clips) lawn grass by rotating a cutter bladeaccommodated in a housing having an opened bottom, along lawn grass tocut the lawn grass. As a technique of such a lawn mower, for example,Japanese Laid-Open Patent Publication No. 2002-315418 is known.

The lawn mower known in Japanese Laid-Open Patent Publication No.2002-315418 includes a housing having an opened bottom, a rotation shaftpositioned inside the housing and extending in a vertical direction ofthe housing, and a narrow and long cutter blade accommodated in thehousing in a manner that the cutter blade is rotatable about therotation shaft. This cutter blade has blades and air lifts at both endsin a longitudinal direction. The blades are formed at front edges in arotation direction of the cutter blade, and the air lifts are formed atrear edges in the rotation direction. When the cutter blades arerotated, the air lifts generate an upward air flow and a swirl air flow.By orienting the lawn grass growing on the lawn ground to stand uprightby the upward air flow, it is possible to cut (clip) the lawn grass bythe cutter blade efficiently. The lawn grass (grass clippings) cut bythe cutter blade is lifted upward, and swirled in the housing by theupward air flow and the swirl air flow generated by the air lifts, andthen, transported into a grass clippings container.

SUMMARY OF THE INVENTION

The characteristics of lawn grass (lawn condition) cut by the lawn moweroften depend on the regional climate. For example, lawn grass containinga large amount of water content is heavy, and lawn grass containing asmall amount of water content is light. That is, there are differentconditions of lawn grass.

Further, even in the case of lawn grass growing on the same area, thelawn grass may have different lawn conditions. The load on the cutterblade is different depending on the lawn condition. As a result, theload on the engine is subject to change. The opening angle of a throttlevalve for the engine is subject to change as well. For example, duringthe lawn mowing operation by the cutter blade, the load on the enginemay be increased due to the rapid change of the lawn condition. In orderto maintain the desired finishing quality of the lawn mowing operation,it is preferable to eliminate unevenness in the lawn grass due to thedifference in the lawn condition. To this end, the human operator isrequired to detect the change in the lawn condition consciously, andthis is laborious. There is a room of further improvement in the workefficiency of the lawn mowing operation.

An object of the present invention is to provide a technique which makesit possible to improve the work efficiency of lawn mowing operation by alawn mower.

In the present invention, a lawn mower includes a cutter blade rotatableabout a rotation shaft extending in a vertical direction, a drive sourceconfigured to drive the cutter blade through the rotation shaft, and agrass clippings container configured to store lawn grass cut by thecutter blade and transported by transportation wind generated by thecutter blade.

Further, the lawn mower includes a flap provided for the cutter blade ina manner that the flap has a flap angle changeable along a horizontalline which is perpendicular (or substantially perpendicular) to therotation shaft, an actuator configured to control the flap angle of theflap, a control unit configured to control the actuator, a grassclippings container weight detection unit configured to detect weight ofthe grass clippings container, and a travel distance detection unitconfigured to detect travel distance of the lawn mower.

The control unit is configured to implement control in a manner thatrotation speed of the drive source and the flap angle of the flap arekept substantially constant over an elapsed time period from time whendetection of the travel distance is started by the travel distancedetection unit to time when travel of predetermined distance iscompleted, determine a change amount of the weight of the grassclippings container detected by the grass clippings container weightdetection unit over the elapsed time period, and implement control in amanner that the rotation speed of the drive source and the flap angle ofthe flap are adjusted in accordance with the change amount of theweight.

Therefore, the control unit determines the change amount of the weightof the grass clippings container over the elapsed time period duringwhich the lawn mower travels by the predetermined distance. If thechange amount of the weight is large, it is possible to presume that thelawn grass (grass clippings) cut by the cutter blade has a lawncondition of heavy weight. If the change amount of the weight is small,it is possible to presume that the lawn grass (grass clippings) cut bythe cutter blade has a lawn condition of light weight. In this manner,it is possible to adjust the rotation speed of the drive source and theflap angle of the flap depending on the characteristics (lawn condition)of the lawn grass cut by the cutter blade.

Therefore, regardless of the lawn condition, by orienting the lawn grassgrowing on the lawn ground to stand upright by the upward air flow, itis possible to cut the lawn grass by the cutter blade efficiently.Further, after the lawn grass (grass clippings) cut by the cutter bladeis lifted upward and swirled in the housing by the upward air flow andthe swirl air flow generated by the flaps, the lawn grass can betransported into the lawn grass clippings container efficiently.Therefore, regardless of the lawn condition, the operator can performthe lawn mowing operation stably and highly efficiently. It is possibleto eliminate unevenness in the clipping of the grass due to thedifference in the lawn condition, without requiring the operator toperform some operation consciously. Consequently, it is possible toimprove the work efficiency of the lawn mowing operation.

Further, by adjusting the rotation speed of the drive source and theflap angle of the flap depending on the characteristics of the lawngrass (lawn condition) cut by the cutter blade, the wind amount of thetransportation wind generated by the cutter blade and the flap changes.Therefore, it is possible to store the grass clippings in the grassclippings container as uniformly as possible. Accordingly, it ispossible to greatly improve the storage ratio of the grass clippingscontainer. It is possible to store the larger quantity of grassclippings in the grass clippings container efficiently.

In the present invention, it is possible to improve the work efficiencyof the lawn mowing operation by the lawn mower.

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings in which a preferredembodiment of the present invention is shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a left side view of a lawn mower of the present invention;

FIG. 2 is a plan view of the lawn mower shown in FIG. 1;

FIG. 3 is a cross sectional view showing a drive source, a cuttermechanism, and an area around a cutter blade shown in FIG. 1;

FIG. 4 is a cross sectional view in which the cutter mechanism and thearea around the cutter blade shown in FIG. 3 are enlarged;

FIG. 5 is an exploded perspective view showing the cutter blade and alower cutter blade shown in FIG. 3;

FIG. 6 is an exploded view showing a cutter blade, a flap, and an areaaround a conversion mechanism shown in FIG. 5;

FIG. 7A is a view showing a first relationship between the flap and theconversion mechanism shown in FIG. 6;

FIG. 7B is a view showing a second relationship between the flap and theconversion mechanism shown in FIG. 6;

FIG. 7C is a view showing a third relationship between the flap and theconversion mechanism shown in FIG. 6;

FIG. 7D is a view showing a fourth relationship between the flap and theconversion mechanism shown in FIG. 6;

FIG. 8 is a schematic diagram of the lawn mower shown in FIG. 1;

FIG. 9 shows the former part of a control flow chart of the control unitshown in FIG. 8;

FIG. 10 shows the latter part of the control flow chart of the controlunit shown in FIG. 8;

FIG. 11 shows a sub-routine of step ST27 of the control flow chart shownin FIG. 10;

FIG. 12 shows an interruption routine of a bag weight change amountdetermination process used in step ST101 of the control flow chart shownin FIG. 11;

FIG. 13 shows an interruption routine of a housing internal pressurechange amount determination process used in step ST102 of the controlflow chart shown in FIG. 11;

FIG. 14 shows the former part of a sub-routine of step ST111 of thecontrol flow chart shown in FIG. 11;

FIG. 15 shows the latter part of a sub-routine of step ST111 of thecontrol flow chart shown in FIG. 11; and

FIG. 16 is a graph showing operation of a lawn mower according to thecontrol unit shown in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment for carrying out the present invention will be describedwith reference to the accompanying drawings.

A lawn mower according to the embodiment will be described withreference to the drawings. It should be noted that, in the followingdescription, the words “front”, “rear”, “left”, “right”, “upper”, and“lower” are used to refer to directions as viewed from a human operator.“Fr” denotes the front side, “Rr” denotes the rear side”, “Le” denotesthe left side, “Ri” denotes the right side, and the “CL denotes” thecenter of the machine width (central line of the machine width).

As shown in FIGS. 1 and 2, a lawn mower 10 is a walk-behind,self-propelled working machine for cutting lawn grass. The lawn mower 10includes a housing 11, left and right wheels 12 provided on the frontside of the housing 11, left and right wheels 13 provided on the backside of the housing 11, a cutter blade 14 accommodated inside the centerof the housing 11 for cutting lawn grass, a drive source 15 (engine 15)provided above the housing 11, and an operation handle 16 extendingbackward from the housing 11. In the following description, a case wherethe drive source 15 is an engine is taken as an example. It should benoted that the drive source 15 is not limited to the engine. Forexample, the drive source 15 may be an electric motor.

As shown in FIG. 2, in a plan view, this lawn mower 10 rotates thecutter blade 14 clockwise by the engine 15 to cut (clip) the lawn grass,and generates flows of the air (swirl air flow or swirl wind) in thehousing 11 as indicated by an arrow Ra. By the swirl air flow, the lawngrass cut by the cutter blade 14 can be delivered to, and stored in agrass clippings container 22 through a grass clippings discharge passage21. For example, the grass clippings container 22 is a bag. Hereinafter,the lawn grass cut (clipped) by the cutter blade 14 will be referred toas the “grass clippings”.

As shown in FIG. 1, this housing 11 is a so-called opened bottom housingwhere only the lower end surface (surface facing the lawn ground Gr) ofthe housing 11 is opened entirely. This housing 11 is a member having aspiral shape in a plan view, i.e., a spiral case (scroll case). Thehousing 11 has a scroll section for swirling the lawn grass cut by thecutter blade 14 by the swirl wind, and transporting the lawn grass(grass clippings) toward the grass clippings discharge passage 21.Structure of this housing 11 is well known (see Japanese Patent No.3771529).

As shown in FIG. 2, a mode switch damper 23 is provided for the grassclippings discharge passage 21. This mode switch damper 23 can beoperated by a damper operation lever 24 (see FIG. 8). This damperoperation lever 24 is a mode switching unit for switching the modeswitch damper 23. Hereinafter, this damper operation lever 24 will alsobe referred to as the “mode switching unit 24” as necessary. Byoperating the damper operation lever 24, it is possible to switch theoperating mode as necessary, between (1) a bagging mode for opening themode switch damper 23 to store the grass clippings in the grassclippings container 22 and (2) a mulching mode for closing the modeswitch damper 23 to discharge the grass clippings to a position belowthe housing 11.

As shown in FIG. 3, this housing 11 also serves as a machine body, andincludes a stand 26 at an upper position. The engine 15 is mounted on anupper end surface of this stand 26. The engine 15 has an output shaft 15a extending from its lower end toward the lawn ground Gr (ground Gr)into the housing 11. The output shaft 15 a is a rotation shaftpositioned above the housing 11, and extends in a vertical direction (inan up-down direction) of the housing 11. Consequently, the output shaft(rotation shaft) 15 a is substantially perpendicular to the horizontallawn ground Gr.

As shown in FIGS. 1 and 3, the left and right rear wheels 13 are traveldrive wheels. That is, the power generated by the engine 15 istransmitted to the left and right rear wheels 13 through a transmission27 (hydraulic continuously variable transmission 27). An input shaft 27a of the hydraulic continuously variable transmission 27 is coupled tothe output shaft 15 a of the engine 15 by a belt 28. This hydrauliccontinuously variable transmission 27 can switch (reverse) the rotationdirection of an output shaft 27 b (wheel shaft 27 b) outputted to therear wheels 13, in response to the rotation direction of the input shaft27 a driven by the engine 15, and switch (change the transmission) ofthe rotation speed of the output shaft 27 b continuously, in response tothe rotation speed of the input shaft 27 a. The structure of thishydraulic continuously variable transmission 27 is well known (e.g., seeJapanese Laid-Open Patent Publication No. 2002-315416).

As shown in FIG. 3, the power generated by the engine 15 is transmittedto a cutter mechanism 40 by a working power transmission system 30. Aclutch 31 and a power transmission mechanism 32 are provided in theworking power transmission system 30 from the engine 15 to a rotationshaft 41 of the cutter mechanism 40. The power transmission mechanism 32is made up of a drive gear 33 and a driven gear 34. The drive gear 33 isattached to the output shaft 15 a of the engine 15 through the clutch31. The driven gear 34 is attached to an upper end 41 b of the rotationshaft 41. These gears 33, 34 are spur gears. When the clutch 31 is inthe OFF state, the rotation shaft 41 is released from the output shaft15 a of the engine 15. When the clutch 31 is in the ON state, therotation shaft 41 is coupled to the output shaft 15 a of the engine 15.Hereinafter, this cutter mechanism 40 and the cutter blade 14 will bedescribed in detail.

As shown in FIG. 4, the cutter mechanism 40 includes the rotation shaft41 and a transmission mechanism 70. This transmission mechanism 70 willbe described later. The rotation shaft 41 extends in a verticaldirection of the housing 11. The rotation shaft 41 is positioned inparallel to the output shaft 15 a of the engine 15. This rotation shaft41 is supported by bearings 42, 43 in a manner that the rotation shaft41 is rotatable but restricted axially with respect to the stand 26.Consequently, the rotation shaft 41 is supported in a manner that therotation shaft 41 is rotatable with respect to the housing 11, andmovement of the rotation shaft 41 in the axial direction is restricted.

The rotation shaft 41 is a hollow shaft. Hereinafter, this rotationshaft 41 will also be referred to as the “hollow shaft 41” as necessary.A lower end 41 a of the rotation shaft 41 is positioned within thehousing 11. The diameter of this lower end 41 a of the rotation shaft 41is larger than the other portion of the rotation shaft 41. The lower end41 a is opened downward to have a substantially cup shape. The openedend surface in the lower end 41 a is closed by a cap 44. The cap 44 isdetachably attached to the lower end 41 a of the rotation shaft 41 by afixing member such as a bolt. The inside of the lower end 41 a and thecap 44 form a space 45.

As shown in FIGS. 4 and 5, the cutter blade 14 is provided for therotation shaft 41, and placed in the housing 11. This cutter blade 14 isa long narrow member having a substantially flat plate shape in a planview, extending in a horizontal line 46 perpendicular to (orsubstantially perpendicular to) the rotation shaft 41. Both ends of thecutter blade 14 in the longitudinal direction have a pair of blades 14a, at front edges of the cutter blade 14 in the rotation direction.

Further, an annular hub 51 is provided at the center of the cutter blade14 in the longitudinal direction. The hub 51 is an annular member fittedto an outer circumferential surface of the lower end 41 a of therotation shaft 41. The hub 51 is detachably attached to the lower end 41a by a fixing member such as a bolt. Therefore, the cutter blade 14 isrotatable together with the rotation shaft 41.

As shown in FIGS. 3, 5, and 6, flaps 52 are formed at least at part ofthe cutter blade 14. The range of the flaps 52 in the cutter blade 14may be any of, only part of the cutter blade 14, the half of the frontend of the cutter blade 14, and the entire cutter blade 14.

For example, the flaps 52 are provided at both ends of the cutter blade14 in the longitudinal direction. The flaps 52 are provided opposite tothe pair of blades 14 a with respect to the cutter blade 14. The cutterblade 14 is cut out for the space required for providing the flaps 52.

The flap angle (upper and lower swing angles) of the flaps 52 can bechanged along the horizontal line 46. More specifically, two flapsupport shafts 53 (as a pair) are provided on the horizontal line 46.The flap support shafts 53 are provided concentrically with each other.One end of each of the pair of flap support shafts 53 extends throughthe hub 51, into the space 45 (see FIG. 4) of the lower end 41 a of therotation shaft 41. Further, the one end of each of the pair of the flapsupport shafts 53 is rotatably supported by the hub 51. The movement ofthe flap support shaft 53 in the axial direction is restricted.

The pair of flaps 52 is attached to the pair of the flap support shafts53. In the structure, the flaps 52 can swing in accordance with rotationof the flap support shafts 53 vertically (direction of the upper andlower surfaces of the flaps 52) about the flap support shafts 53. Thatis, the flaps 52 are auxiliary blades that can swing up and down alongthe horizontal line 46 (in the longitudinal direction of the cutterblade 14). Hereinafter, the flaps 52 will also be referred to as the“auxiliary blades 52” as necessary.

As shown in FIGS. 3 and 4, the flap angle of the flaps 52 is controlledby an output from an actuator 60. That is, the output of the actuator 60is transmitted to the flaps 52 by the transmission mechanism 70. Thistransmission mechanism 70 is accommodated inside the hollow shaft 41(rotation shaft 41). The transmission mechanism 70 is made up of acontrol shaft 71 and a conversion mechanism 80.

The control shaft 71 is slidable in the axial direction with respect tothe hollow shaft 41, and relative rotation of the control shaft 71 withrespect to the hollow shaft 41 is restricted, and the control shaft 71is fitted into the hollow shaft 41. Specifically, the control shaft 71is slidable along the hollow shaft 41 by a spline 72, and relativerotation of the control shaft 71 is restricted. It should be noted thatthe control shaft 71 may adopt structure using serration or parallelkeys instead of the spline 72.

The actuator 60 is a linear actuator. That is, an output shaft 60 a ofthe actuator 60 is slidable in the axial direction of the control shaft71. The output shaft 60 a and the control shaft 71 are positionedconcentrically with respect to the hollow shaft 41.

The output shaft 60 a of the actuator 60 is combined with an upper end71 a of the control shaft 71 in a manner that the control shaft 71 canbe driven to move in a sliding manner. More specifically, a recess 73having a circular shape in cross section is formed at an upper end ofthe control shaft 71. The recess 73 is opened upward. The output shaft60 a of the actuator 60 is fitted to the recess 73.

Two roller bearings 74, 75 are interposed between the output shaft 60 aof the actuator 60 and the control shaft 71. One of the roller bearings74, 75 is a radial bearing 74, and the other of the roller bearings 74,75 is a thrust bearing 75. It should be noted that the two rollerbearings 74, 75 may comprise needle bearings. The outer circumferentialsurface of the output shaft 60 a is supported by the radial bearing 74in a manner that the outer circumferential surface of the output shaft60 a is rotatable, and slidable on the inner circumferential surface ofthe recess 73. The lower end surface of the output shaft 60 a rotatablycontacts the bottom surface of the recess 73 through the thrust bearing75. The output shaft 60 a moves down to displace the control shaft 71 ina sliding manner through the thrust bearing 75.

A lower end 71 b of the control shaft 71 extends into the space 45, andfaces an upper surface of the cap 44. A compression coil spring 76(return spring 76) is interposed between the lower end surface of thecontrol shaft 71 and the upper surface of the cap 44. The compressioncoil spring 76 biases the control shaft 71 toward the lower end surfaceof the output shaft 60 a of the actuator 60. In the structure, the lowerend surface of the output shaft 60 a contacts the bottom surface of therecess 73 through the thrust bearing 75 all the time. As the outputshaft 60 a moves upward, the compression coil spring 76 can displace thecontrol shaft 71 upward in a sliding manner. Consequently, the controlshaft 71 is synchronized with forward/backward movement of the outputshaft 60 a of the actuator 60, and can slide vertically in the samedirection as the output shaft 60 a.

The conversion mechanism 80 is capable of converting the slide movementof the control shaft 71 into movement to change the flap angle of theflaps 52, i.e., swing movement, and the conversion mechanism 80 isaccommodated inside the hollow shaft 41 (i.e., the space 45). That is,the lower end 71 b of the control shaft 71 is coupled to the flaps 52through the conversion mechanism 80.

As shown in FIGS. 4 to 7D, this conversion mechanism 80 includes a pin81 and a pair of cams 82. The pin 81 extends outside toward both sidesin the radial direction from the lower end 71 b of the control shaft 71.For example, the pin 81 passes through the lower end 71 b in the radialdirection.

The two cams 82 (as a pair) are circular disk members. Each of the cams82 is connected to one end of each of the pair of flap support shafts53. The pair of cams 82 is rotatable about the pair of the flap supportshafts 53, and supported at the lower end 41 a of the rotation shaft 41.As described above, the pair of cams 82 is rotatably supported by thehollow shaft 41 about a swing center 52 a (horizontal line 46) of theflaps 52, and provided at the flaps 52 by the flap support shafts 53.

The cams 82 have cam surfaces 83 which can contact the pin 81. The camsurfaces 83 face each other. The front end of the pin 81 can contact thecam surfaces 83. These cam surfaces 83 are formed by cam grooves whichare configured to convert the sliding movement of the pin 81 which isdisplaced vertically together with the control shaft 71 into therotation movement of the cams 82. Hereinafter, the cam surfaces 83 willalso be referred to as the “cam grooves 83” as necessary. The outercircumferential surface of the pin 81 slides along the side surfaces ofthe cam grooves 83, and can be displaced vertically. As a result, thecam 82 is rotated.

As shown in FIGS. 6 and 7A, this cam groove 83 is formed around theswing center 52 a of the flap 52, and has a V-shape orientedsubstantially in a lateral direction. In this regard, the swing center52 a of the flap 52 is in alignment with a center 53 a of the flapsupport shaft 53 and a rotation center 82 a of the cam 82. The swingcenter 52 a of the flap 52 is positioned along the horizontal line 46perpendicular to the rotation shaft 41. More specifically, the camgroove 83 includes a groove center 84 positioned on the rotation center82 a of the cam 82, an upper groove 85 extending upward obliquely fromthe groove center 84, and a lower groove 86 extending downward obliquelyfrom the groove center 84. The groove center 84, the upper groove 85,and the lower groove 86 are continuous.

Next, operation relationship between the conversion mechanism 80 and theflaps 52 will be described with reference to FIGS. 7A to 7D. FIG. 7Ashows the relationship between the conversion mechanism 80 and the flap52 when the flap 52 is in the horizontal state (flap angle θr=0°). Atthis time, the pin 81 is positioned at the groove center 84 (therotation center 82 a of the cam 82). The cutter blade 14 is rotated in adirection indicated by an arrow Rb together with the flap 52 in thehorizontal state. Thus, the cutter blade 14 can cut (clip) the lawngrass.

Thereafter, the pin 81 is displaced downward (in a direction indicatedby an arrow Ad) together with the control shaft 71 shown in FIG. 6, topush the side wall of the lower groove 86 of the cam groove 83 downward.Since the cam 82 and the flap support shaft 53 are rotated clockwise,the flap 52 swings upward. The result is shown in FIG. 7B. The degree ofthe swing angle θr at which the flap 52 swings from the horizontalstate, i.e., the degree of the flap angle θr corresponds to the downwarddisplacement amount of the control shaft 71. By rotation of the cutterblade 14, the flap 52 generates upward air flow Rc.

Thereafter, the pin 81 is displaced upward (in a direction indicated byan arrow Au) together with the control shaft 71 shown in FIG. 6. The pin81 is in the so-called “missed swing” state where the pin 81 is onlydisplaced upward in the lower groove 86 until the pin 81 returns to thegroove center 84. Therefore, the flap angle θr of the flap 52 does notchange.

Thereafter, as shown in FIG. 7C, the pin 81 is displaced further upwardfrom the groove center 84 (in a direction indicated by an arrow Au) topush the side wall of the upper groove 85 upward. Since the cam 82 andthe flap support shaft 53 are rotated counterclockwise in the drawing,the flap 52 swings downward. The result is shown in FIG. 7D. The flap 52returns to the horizontal state (flap angle θr=0°).

The above explanation is summarized below. As shown in FIGS. 4, 5, 7A to7D, the lawn mower 10 includes the flaps 52 (auxiliary blades 52)provided along the horizontal line 46, at least at part of the cutterblade 14 in a manner that the flap angle θr (swing angle θr) can bechanged, the actuator 60 having (generating) an output to control theflap angle θr of the flaps 52, and the transmission mechanism 70 fortransmitting the output of the actuator 60 to the flaps 52.

Therefore, the flap angle θr of the flaps 52 of the cutter blade 14 canbe set to the optimum angle by the actuator 60 as necessary inaccordance with the working condition of the lawn mower 10. Thus, swirlwind can be generated by the flaps 52 efficiently, in accordance withthe working condition for lawn mowing operation. The grass clippings canbe swirled by the swirl wind efficiently in the housing 11, andtransported into the grass clippings container 22 (see FIG. 2)efficiently. Accordingly, it is possible to improve the energyconsumption efficiency in the drive source (power source) 15 for drivingthe cutter blade 14. Further, it is not necessary to change the rotationspeed of the cutter blade 14.

Further, it is possible to control the flap angle θr of the flaps 52 inaccordance with the load state of the cutter blade 14 and/or thenegative pressure state in the housing 11. By controlling the flap angleθr of the flaps 52, it is possible to sufficiently suppress the jammingphenomenon of the grass clippings which may occur in the transportationpath of the grass clippings from the housing 11 to the grass clippingscontainer 22.

Further, during the operation at low load where, e.g., the cutter blade14 is rotated idly, and no grass clipping operation is performed, bydecreasing the flap angle θr of the flaps 52, it is possible to reducethe noises such as wind noises. Further, it is possible to improve thenoise suppression performance regardless of the rotation speed of thecutter blade 14.

Further, when the grass clippings are blown by the swirl wind to storethe grass clippings in the grass clippings container 22, by setting theflap angle θr of the flaps 52 as necessary, it is possible to adjust thedistance by which the grass clippings fly over the swirl wind.Consequently, it is possible to efficiently store the grass clippings inthe grass clippings container 22.

Further, as shown in FIG. 4, the transmission mechanism 70 isaccommodated inside the hollow shaft 41. That is, the transmissionmechanism 70 is provided by utilizing the rotation shaft 41 effectively.By accommodating the transmission mechanism 70 in the hollow rotationshaft 41, it is possible to efficiently provide the transmissionmechanism 70 in a compact space in the housing 11 efficiently. Further,since the transmission mechanism 70 is not exposed into the housing 11,there is no concern of jamming between the transmission mechanism 70 andthe housing 11. Further, the swirl wind generated by the cutter blade 14or the flaps 52 can flow smoothly into the housing 11 without beingobstructed by the transmission mechanism 70. Therefore, though thetransmission mechanism 70 is present, it is possible to store the grassclippings efficiently in the grass clippings container 22 by allowingthe grass clippings to fly over the swirl wind which flows smoothly.

Further, as shown in FIG. 4, the transmission mechanism 70 includes thecontrol shaft 71 and the conversion mechanism 80. The lower end 71 b ofthe control shaft 71 is coupled to the flaps 52 through the conversionmechanism 80. The output shaft 60 a of the actuator 60 is combined withthe upper end 71 a of the control shaft 71 in a manner that the controlshaft 71 can be driven to move in a sliding manner. Thus, the controlshaft 71 is driven by the actuator 60 to move in a sliding manner, andthe sliding movement of the control shaft 71 can be converted by theconversion mechanism 80 into movement to change the flap angle θr of theflaps 52. As a result, the flap angle θr can be controlled by theactuator 60. Further, the transmission mechanism 70 is made up of thecontrol shaft 71 fitted into the hollow shaft 41 in a slidable manner inthe axial direction, and the conversion mechanism 80 accommodated insidethe hollow shaft 41. Therefore, the transmission mechanism 70 can beaccommodated efficiently in the rotation shaft 41, by effectivelyutilizing the inner space of the hollow rotation shaft 41.

Further, as shown in FIG. 4, by the cam mechanism made up of the pin 81and the cams 82, it is possible to form the simple and compactconversion mechanism 80. Further, the sliding movement of the controlshaft 71 can be converted into movement of changing the flap angle θr ofthe flaps 52 promptly.

Further, as shown in FIGS. 4 and 6, the cam groove 83 is formed in aV-shape substantially oriented laterally, around the swing center 52 aof the flaps 52. In the structure, by changing the slide direction ofdriving the control shaft 71 by the actuator 60, it is possible tochange the swing direction of the flaps 52. For example, the swingdirection of the flaps 52 can be changed from upward to downward. Inthis case, by reversing rotation of the rotation shaft 41, it ispossible to generate an upward air flow by the flaps 52. As describedabove, the swing direction of the flaps 52 and the rotation direction ofthe rotation shaft 41 can be combined as necessary, in accordance withthe usage condition of the lawn mower 10.

Further, as shown in FIG. 4, the roller bearings 74, 75 are interposedbetween the output shaft 60 a of the linear actuator 60 and the controlshaft 71. In the structure, when the control shaft 71 and the hollowshaft 41 are rotated together, the frictional resistance between theoutput shaft 60 a of the linear actuator 60 and the control shaft 71 canbe reduced as much as possible. Therefore, even if the control shaft 71is rotated at high speed, it is possible to promptly and reliably drivethe control shaft 71 to move in a sliding manner by the linear actuator60. Even during rotation of the cutter blade 14, it is possible to setthe flap angle θr of the flaps 52 promptly and reliably to the optimumangle in accordance with the working condition of the lawn mower 10.

In this regard, when the cutter blade 14 having the flaps 52 shown inFIGS. 1 and 3 is rotated, it is possible to generate the upward air flowby the flaps 52. The magnitude of this upward air flow depends on thedegree of the flap angle θr of the flaps 52. Negative pressure isgenerated below the cutter blade 14 by the upward air flow. Incorrespondence with the magnitude of this negative pressure, the degreein which the lawn grass growing on the lawn ground Gr (ground Gr) standsupright changes. For ensuring that the lawn grass after lawn mowingoperation has a constant height as much as possible, it is morepreferable to adjust the height of the housing 11 having the cutterblade 14 finely.

In this regard, as shown in FIGS. 4 and 5, a lower cutter blade 91 ispositioned below the cutter blade 14. This lower cutter blade 91comprises a fixed blade fixed to the rotation shaft 41 (hollow shaft41). That is, the lower cutter blade 91 is removably attached to the cap44 by a fixing member such as a bolt. In the structure, the lower cutterblade 91 is rotatable together with the rotation shaft 41. This lowercutter blade 91 is a narrow and long member having a substantially flatplate shape in a plan view, and basically extends along the cutter blade14. This lower cutter blade 91 may be positioned in slightly out ofphase with the cutter blade 14. Two blades 91 a (as a pair) are providedat both ends of the lower cutter blade 91 in the longitudinal direction.The blades 91 a are formed on the front edges of the lower cutter blade91 in the rotation direction Rb.

Therefore, the magnitude of the negative pressure generated below thelower cutter blade 91 by the upward air flow is substantially constant.The degree in which the lawn grass growing on the lawn ground Gr (groundGr) stands upright is substantially constant. It is possible to keep theheight of lawn grass after lawn mowing operation as constant aspossible.

Therefore, it is possible to efficiently generate the swirl wind by theflaps 52 of the upper cutter blade 14, and ensure that the lawn grasshas the constant height after lawn mowing operation by the lower cutterblade 91 as much as possible.

As shown in FIGS. 1 and 8, the operation handle 16 has a substantiallyarch shape as viewed from the back side of the lawn mower 10, andincludes left and right handle bars 16 a extending backward, and upwardfrom the housing 11, and a grip 16 b bridging the left and right handlebars 16 a. A clutch lever 101 and a travel lever 102 are attached to arear end of the left and right handle bars 16 a in a manner that theclutch lever 101 and the travel lever 102 can swing back and forth. Theclutch lever 101 and the travel lever 102 have a substantially archshape along the back side of the operation handle 16, as viewed from theback side of the lawn mower 10. The clutch lever 101 and the travellever 102 can be gripped together with the grip 16 b by a hand whenswung to the front side. The clutch lever 101 and the travel lever 102are automatic return type operation members, such that when these levers101, 102 are released from the hand, the levers 101, 102 return to theiroriginal positions automatically.

The clutch lever 101 is an operation member for switching the clutch 31.Only in the state where the clutch lever 101 and the grip 16 b aregripped together by the hand, the clutch 31 is placed in the ON state.As a result, the cutter blade 14 can be placed in the operating state.When the clutch lever 101 is released from the hand, the clutch 31automatically returns to the OFF state. As a result, the cutter blade 14can be placed in the stop state.

The operation position of the clutch lever 101 is detected by a clutchoperation detection sensor 103. For example, the clutch operationdetection sensor 103 may comprise a switch. When the clutch 31 isswitched on by the clutch lever 101, i.e., when the cutter blade 14 isswitched to the operating state, the clutch operation detection sensor103 detects an operation switch position, and outputs an operationswitch signal. When the clutch 31 is turned off by the operation clutchlever 101, i.e., when the cutter blade 14 is switched to the stop state,the clutch operation detection sensor 103 detects an operation stopswitch position to output a stop switch signal. The combinationstructure of the clutch lever 101 and the clutch operation detectionsensor 103 constitutes a blade switching unit 104.

As long as the blade switching unit 104 can perform switching of thecutter blade 14 between the operating state and the stop state, theblade switching unit 104 may have any structure. For example, the bladeswitching unit 104 only includes an operation switch. By the operationswitch, it is possible to electrically switch the state of the clutch 31between ON and OFF. In this case, when the operation switch switches theclutch 31 to the ON state, i.e., switches the cutter blade 14 to theoperating state, the operation switch outputs an operation switchsignal. In this case, when the operation switch switches the clutch 31to the OFF state, i.e., switches the cutter blade 14 to the stop state,the operation switch outputs a stop switch signal.

Hereinafter, the blade switching unit 104 (including the operationswitch) will also be referred to as the “blade switch 104” as necessary.

A shift lever 105 is provided on the back side of the left or righthandle bar 16 a. The shift lever 105 performs transmission operation ofthe transmission 27. The shift lever 105 is connected to the travellever 102 through a tension spring 106, and coupled to a transmissionarm of the transmission 27 through a transmission cable 107. When thetravel lever 102 is operated, the transmission 27 rotates the rearwheels 13 at the speed in correspondence with the transmission operationposition of the shift lever 105. Thereafter, the travel lever 102 isreturned to its original position, and the output rotation of thetransmission 27 becomes zero, and the rear wheels 13 are stopped.

The lawn mower 10 includes an internal pressure detection unit 111, atravel speed detection unit 112, a grass clippings container weightdetection unit 113, a mode switch 114, a flap angle detection unit 115,an operation unit 116, and a control unit 117. The operation unit 116and the control unit 117 are positioned adjacent to the engine 15 (drivesource 15) or at the operation handle 16. The operation unit 116includes a main switch 118 and an alarm 119.

The internal pressure detection unit 111 detects the internal pressurePr of the housing 11, and outputs a detection signal. For example, theinternal pressure detection unit 111 is positioned between the housing11 and the mode switch damper 23, in the grass clippings dischargepassage 21.

The travel speed detection unit 112 detects the travel speed Spr(vehicle velocity Spr) of the lawn mower 10, and outputs a detectionsignal. For example, the travel speed detection unit 112 detects therotation speed of the wheel shaft 27 b of the rear wheels 13 toindirectly detect the vehicle velocity Spr of the lawn mower 10.

The grass clippings container weight detection unit 113 detects theweight Wr of the grass clippings container 22, and outputs a detectionsignal. For example, the grass clippings container weight detection unit113 detects the weight Wr of the grass clippings container 22 directlyor indirectly. The grass clippings container 22 is detachably attachedto the outlet of the grass clippings discharge passage 21. The weight Wrof the grass clippings container 22 is applied to this outlet. Further,moment of this weight Wr is applied to the outlet. In accordance withthe magnitude of this moment, the grass clippings container 22 attemptsto swing (rotate) downward relative to the outlet. By detecting thisswing angle (rotation angle), the grass clippings container weightdetection unit 113 can detect the weight Wr of the grass clippingscontainer 22 indirectly. Further, by detecting the weight Wr applied tothe outlet, the grass clippings container weight detection unit 113 candetect the weight Wr of the grass clippings container 22 indirectly.Moreover, the grass clippings container weight detection unit 113 may beconfigured to directly detect the weight Wr of the grass clippingscontainer 22.

The mode switch 114 detects a switch position of the mode switch damper23, and outputs a detection signal. That is, the mode switch 114 is amode switch detection unit for outputting a switch signal correspondingto opening/closing of the mode switch damper 23. Hereinafter, the modeswitch 114 will also be referred to as the “mode switch detection unit114” as necessary. This mode switch 114 directly detects anopening/closing position of the mode switch damper 23 or detects a leverposition of the damper operation lever 24 to indirectly detect theopening/closing position of the mode switch damper 23. Then, after themode switch 114 detects that the mode switch damper 23 is at an openposition, the mode switch 114 outputs an open signal, i.e., a baggingmode signal. Further, after the mode switch 114 detects that the modeswitch damper 23 is at a closed position, the mode switch 114 outputs aclose signal, i.e., a mulching mode signal.

The mode switching unit 24 is not limited to the damper operation lever.Power means such as an electric motor may be used as the mode switchingunit 24. In such a case, the mode switching unit 24 comprising the powermeans can be switched by the mode switch 114. The mode switch 114 inthis case plays a role of the “mode switch detection unit” foroutputting a switch signal in correspondence with opening/closing of themode switch damper 23, and additionally, plays a role of the “operationswitch” for switching the mode switching unit 24 comprising the powermeans.

In this case, when the mode switch damper 23 is operated by the modeswitch detection unit 114 (mode switch 114) comprising the operationswitch, for switching to the open position, the mode switch detectionunit 114 outputs the bagging mode signal. Further, when the mode switchdamper 23 is operated by the mode switch detection unit 114, forswitching to the closed position, the mode switch detection unit 114outputs the mulching mode signal.

The flap angle detection unit 115 detects the flap angle θr of the flaps52, and outputs a detection signal. For example, the flap angledetection unit 115 detects the axial position of the output shaft 60 aof the actuator 60, the axial position of the control shaft 71, and therotation angle of the flap support shaft 53 shown in FIG. 3 toindirectly detect the flap angle θr of the flaps 52.

The main switch 118 comprises a rotary switch for turning on/off thepower supply system of the lawn mower 10. For example, in the case wherethe drive source 15 comprises an engine, the main switch 118 comprisesan ignition switch. The ignition switch 118 (main switch 118) is capableof switching among an OFF position, an ON position, and a startposition.

By operating the ignition switch 118 for switching from the OFF positionto the ON position, the power supply system of the lawn mower 10 isturned on to prepare for starting operation of the engine 15.

By operating the ignition switch 118 for switching from the ON positionto the start position (ST position), it is possible to start operationof the engine 15. After operation of the engine 15 is started, theignition switch 118 is returned from the start position to the ONposition.

By returning the ignition switch 118 from the ON position to the OFFposition, it is possible to stop operation of the engine 15, and stopthe power supply system of the lawn mower 10.

As described above, the main switch 118 is operated for switchingbetween the start and stop of operating the engine 15 (drive source 15).Hereinafter, the main switch 118 (ignition switch 118) will also bereferred to as the “drive source operation switch 118” as necessary.

The alarm 119 issues notifications visually or by outputting sounds inaccordance with instructions from the control unit 117.

Next, the system of the engine 15 will be described. The engine 15includes a throttle valve control motor 121, a throttle opening angledetection unit 122, and an engine speed detection unit 123. The throttlevalve control motor 121 is an actuator for opening/closing a throttlevalve 125 of an engine intake system 124. For example, the throttlevalve control motor 121 is a step motor. The throttle opening angledetection unit 122 detects the opening angle αr of the throttle valve125, and outputs a detection signal.

The engine speed detection unit 123 detects the rotation speed Ner(rotation number Ner) of the engine 15, and outputs a detection signal.When the engine 15 (drive source 15) in the rotating state is stopped,the value of the rotation speed Ner becomes substantially “zero”. Whenthe engine speed detection unit 123 detects that the value of therotation speed Ner becomes substantially “zero”, i.e., detects that theengine 15 (drive source 15) in the rotating state has been stopped, theengine speed detection unit 123 outputs a drive source stop signal.Hereinafter, the engine speed detection unit 123 will also be referredto as the “drive source stop detection unit 123” as necessary.

The control unit 117 is an electronic control unit for controlling theengine 15 in a predetermined control mode by receiving signals from themain switch 118 or various detection units. For example, the controlunit 117 is a microcomputer. That is, based on various items of datasuch as the detected rotation speed Ner of the engine 15 and the openingangle αr of the throttle valve 125, by controlling the opening angle αrof the throttle valve 125 through the throttle valve control motor 121in a predetermined control mode, electrical control is implemented in amanner that the rotation speed Ner of the engine 15 matches the targetrotation speed. Further, the control unit 117 electrically controls theflap angle θr of the flaps 52 by receiving signals from the main switch118 and/or various detection units.

As can be seen from the above explanation, the engine 15 ischaracterized by mounting an electronic governor 126 (also referred toas the electric governor, or electric speed governor). The electronicgovernor 126 controls the rotation speed Ner of the engine 15 based onthe control signal from the control unit 117 by automatically adjustingthe opening angle αr of the throttle valve 125 by the throttle valvecontrol motor 121. The electronic governor 126 is made up of combinationof the control unit 117, the throttle valve control motor 121, thethrottle opening angle detection unit 122, the engine speed detectionunit 123, and the throttle valve 125.

Next, the control flow in the case where the control unit 117 (see FIG.8) comprises a microcomputer will be described with reference to FIGS. 9to 15. In the control flow chart shown in FIGS. 9 to 15, among the stepsfor controlling the lawn mower 10, only the steps regarding control ofthe rotation speed Ner of the drive source 15 and the flap angle θr ofthe flaps 52 will be described, and explanation about the stepsregarding other items of control is omitted. Further, in this controlflow, explanation about a case where the drive source 15 is an engine,and the main switch 118 is an ignition switch will be given as anexample. Hereinafter, the explanation will be given with reference toFIGS. 3, 4, and 8.

FIGS. 9 and 10 show a control flow chart of the control unit 117according to the present invention. When control is started, firstly, instep ST10, the control unit 117 performs initialization for setting eachof setting values and flags to an initial value. For example, a bladeswitch flag Fa is set to “0”, and an initial value flag Fb is set to“0”.

Next, operation of the engine 15 is started (step ST11). Operation ofthe engine 15 is started when the main switch 118 is operated forswitching from an ON position to a start position. Then, a signal of themode switch 114 is read (step ST12).

Next, it is determined whether the lawn mower 10 is operated in thebagging mode or the mulching mode (step ST13). If a signal indicatingthat the mode switch damper 23 is opened is received from the modeswitch 114, it is determined that the lawn mower 10 is operated in thebagging mode. If a signal indicating that the mode switch damper 23 isclosed is received from the mode switch 114, it is determined that thelawn mower 10 is operated in the mulching mode.

At this time, if it is determined that the lawn mower 10 is operated inthe mulching mode, the control proceeds to step ST14. In step ST14,after the mulching mode control process is performed, the control flowincluding the series of operations is finished. In the mulching mode,the grass clippings cut by the cutter blade 14 can be discharged to aposition below the housing 11.

In step ST13, if it determined that lawn mower 10 is operated in thebagging mode, the control proceeds to step ST15. In step ST15, a signalof the blade switch 104 is read.

Next, it is determined whether or not the blade switch 104 is on (stepST16). At this time, if it is determined that the blade switch 104 isoff, the control proceeds to step ST17.

In this step ST17, the value of the accumulated distance La is reset to0 (La=0). This accumulated distance La will be described later. In thenext step ST18, the setting value of the target opening angle αs(reference opening angle αs) of the throttle valve 125 is set to apredetermined first reference opening angle α1 (αs=α1). In the next stepST19, the target rotation speed setting value Nes of the engine 15 isset to a predetermined first reference rotation speed N1 (Nes=N1). Inthe next step ST20, the target flap angle setting value θs of the flaps52 is set to 0° (θs=0°). In the next step ST21, after the blade switchflag Fa is set to “0”, the control proceeds to step ST28. In thismanner, when the blade switch 104 is off, in steps ST17 to ST21, initialvalues of the elements when operation of the cutter blade 14 is stoppedare set.

In the meanwhile, in step ST16, if it is determined that the bladeswitch 104 is on, the control proceeds to step ST22. In step ST22, it isdetermined whether or not the blade switch flag Fa is “0” (Fa=0). If itis determined that the flag Fa=0, the control proceeds to step ST23.

In step ST23, the setting value of the target opening angle αs(reference opening angle αs) of the throttle valve 125 is set to apredetermined second reference opening angle α2 (αs=α2). The secondreference opening angle α2 is larger than the first reference openingangle α1 in step ST18 by a predetermined opening angle (α2>α1).

In the next step ST24, the target rotation speed setting value Nes ofthe engine 15 is set to a predetermined second reference rotation speedN2 (Nes=N2). The second reference rotation speed N2 is higher than thefirst reference rotation speed N1 in the above step ST19 by apredetermined speed (N2>N1).

In the next step ST25, the target flap angle setting value θs of theflaps 52 is set to a predetermined first reference flap angle θ1(θs=θ1). The first reference flap angle θ1 is larger than 0°. In thenext step ST26, after the blade switch flag Fa is set to “1”, thecontrol proceeds to step ST28.

In this manner, when the blade switch 104 is on, if the blade switchflag Fa is “0”, in steps ST23 to ST26, basic values of the elementsduring rotation of the cutter blade 14 are set.

In the above step ST22, if it is determined that the blade switch flagFa is not “0” (Fa≠0), the control proceeds to step ST27. In step ST27,after the determination process based on the change amount of the weightof the grass clippings container 22 (bag 22), the control proceeds tostep ST28. Specific control flow for performing the determinationprocess based on the weight change amount in this step ST27 will bedescribed with reference to FIG. 11.

In the next step ST28, the throttle valve control motor 121 iscontrolled until the actual opening angle αr (net opening angle αr) ofthe throttle valve 125, which is detected by the throttle opening angledetection unit 122, becomes equal to the target opening angle αs, i.e.,αr=αs.

In the next step ST29, the actual rotation speed Ner (net rotation speedNer) of the engine 15 detected by the engine speed detection unit 123 iscontrolled until it becomes equal to the target rotation speed settingvalue Nes (target rotation speed Nes), i.e., Ner=Nes.

In the next step ST30, the actuator 60 is controlled until the actualflap angle θr (net flap angle θr) of the flaps 52 detected by the flapangle detection unit 115 becomes equal to the target flap angle θs(target flap angle setting value θs), i.e., θr=θs.

Next, a switch signal of the main switch 118 is read (step ST31). Next,it is determined whether or not the main switch 118 has been operatedfor switching to an OFF position (step ST32). As long as it isdetermined that the main switch 118 has not been operated for switchingto the OFF position, the control returns to step ST15 to repeat thesesteps ST15 to ST32. In the meanwhile, in step ST32, if it is determinedthat the main switch 118 has been operated for switching to the OFFposition, this control flow is finished.

FIG. 11 is a sub-routine for carrying out the determination processbased on the change amount in the weight of the grass clippingscontainer 22 (bag 22) shown in the above step ST27 of FIG. 10.

Firstly, in step ST101, it is determined whether or not the changeamount ΔWr per predetermined fixed time Δt1, of the weight Wr detectedby the grass clippings container weight detection unit 113 has beenincreased to a predetermined weight change amount reference value ΔWs(ΔWr≧ΔWs). This change amount ΔWr is determined successively everypredetermined fixed minute time by an interruption routine (bag weightchange amount determination process), e.g., shown in FIG. 12. Thisinterruption routine will be described later.

In step ST101, if it is determined that the change amount ΔWr is belowthe weight change amount reference value ΔWs (ΔWr<ΔWs), i.e., if it isdetermined that the change amount ΔWr has not been increased to thepredetermined weight change amount reference value ΔWs, the controlproceeds to the next step ST102. In this step ST102, it is determinedwhether or not the change amount ΔPr per predetermined fixed time Δt2 ofthe internal pressure Pr detected by the internal pressure detectionunit 111 has been increased to a predetermined internal pressure changeamount reference value ΔPs (ΔPr≧ΔPs). For example, the fixed time Δt2 isthe same as the fixed time Δt1. This change amount ΔPr is determinedsuccessively every predetermined fixed minute time by an interruptionroutine (housing internal pressure change amount determination process),e.g., shown in FIG. 13. This interruption routine will be describedlater.

In this step ST102, if it is determined that the change amount ΔPr percertain fixed time Δt2 of the internal pressure Pr has been increased tothe internal pressure change amount reference value ΔPs (ΔPr≧ΔPs), instep ST103, the target flap angle indication value θb of the flaps 52 isset to 0° (θb=0°), and then, the control proceeds to step ST104. In stepST104, control is implemented to drive the alarm 119, and then, thecontrol returns to step ST27 of FIG. 10. In the meanwhile, in stepST102, if it is determined that the change amount ΔPr has not beenincreased to the internal pressure change amount reference value ΔPs(ΔPr<ΔPs), control directly returns to step ST27 of FIG. 10.

In this regard, a condition where “the change amount ΔWr of the weightWr per fixed time Δt1 is below the weight change amount reference valueΔWs (ΔWr<ΔWs)” determined in step ST101 will be referred to as the“first condition”. Further, a condition where “the change amount ΔPr perpredetermined fixed time Δt2 of the internal pressure Pr has beenincreased to the internal pressure change amount reference value ΔPs(ΔPr≧ΔPs)” determined in step ST102 will be referred to as the “secondcondition”. If it is determined that the two conditions (the firstcondition and the second conditions) are satisfied, the control unit 117controls the actuator 60 in a manner that the flaps 52 are placed in asubstantially horizontal state (see ST103 and ST30 in FIG. 10), anddrives the alarm 119 (see step ST104).

In step ST101, if it is determined that the change amount ΔWr has beenincreased to the weight change amount reference value ΔWs (ΔWr≧ΔWs), thecontrol proceeds to step ST105.

In this step ST105, the actual weight Wr (net weight Wr) of the grassclippings container 22 is detected by the grass clippings containerweight detection unit 113. Next, the value of the net weight Wr iscompared with the first weight reference value Wd and the second weightreference value Wu (step ST106). The first weight reference value Wd issmaller than the second weight reference value Wu.

In step ST106, if it is determined that the net weight Wr is equal to orsmaller than the first weight reference value Wd (Wr≦Wd), the controlproceeds to step ST110 directly.

In step ST106, if it is determined that the net weight Wr exceeds thefirst weight reference value Wd and equal to or less than the secondweight reference value Wu (Wr<Wd≦Wu), the control proceeds to stepST107. In step ST107, the target flap angle indication value θb of theflaps 52 is set to a predetermined second reference flap angle θ2(θb=θ2), and then, the control proceeds to step ST110. This secondreference flap angle θ2 is larger than the first reference flap angle θ1by a predetermined angle (θ2>θ1).

In step ST107, if it is determined that the net weight Wr exceeds thesecond weight reference value Wu (Wu<Wr), the control proceeds to stepST108. In step ST108, the target rotation speed setting value Nes is setto the third reference rotation speed N3 (Nes=N3). This third referencerotation speed N3 is higher than the second reference rotation speed N2in the above step ST24 by a predetermined speed (N3>N2). Then, in stepST109, the target flap angle indication value θb of the flaps 52 is setto the predetermined reference flap angle θ3 (θb=θ3), and then, thecontrol proceeds to step ST110. This reference flap angle θ3 is largerthan the second reference flap angle θ2 by a predetermined angle(θ3>θ2).

In step ST110, after the process of correcting the rotation speed of theengine 15 and the flap angle of the flaps 52 is performed, the controlreturns to step ST27 of FIG. 10. Specific control flow for performingthe process of correcting the rotation speed of the engine 15 and theflap angle of the flaps 52 in step ST110 will be described withreference to FIG. 14.

FIG. 12 is a control flow diagram of the interruption routine of the bagweight change amount determination process, for determining the changeamount ΔWr of the weight Wr of the grass clippings container 22.

After this interruption routine is started, firstly, in step ST201, thenet weight Wr of the grass clippings container 22 is detected by thegrass clippings container weight detection unit 113 (first detection).The net weight Wr at this time will be referred to as the “first weightW1”. In the next step ST202, predetermined fixed time Δt1 is counted. Inthe next step ST203, the net weight Wr of the grass clippings container22 is detected by the grass clippings container weight detection unit113 (second detection). The net weight Wr at this time will be referredto as the “second weight W2”.

In the next step ST204, the difference ΔWr between the first weight W1and the second weight W2, i.e., the change amount ΔWr per predeterminedfixed time Δt1, of the weight Wr is determined (ΔWr=W2−W1). Thereafter,this interruption routine is finished.

FIG. 13 shows a control flow diagram of the interruption routine of thehousing internal pressure change amount determination process, fordetermining the change amount ΔPr of the internal pressure Pr of thehousing 11.

After this interruption routine is started, firstly, in step ST301, thenet internal pressure Pr of the housing 11 is detected by the internalpressure detection unit 111 (first detection). The net internal pressurePr at this time will be referred to as the “first internal pressure P1”.In the next step ST302, predetermined fixed time Δt2 is counted. In thenext step ST303, the net internal pressure Pr of the housing 11 isdetected by the internal pressure detection unit 111 (second detection).The net internal pressure Pr at this time will be referred to as the“second internal pressure P2”.

In the next step ST304, the difference ΔPr between the first internalpressure P1 and the second internal pressure P2, i.e., the change amountΔPr per predetermined fixed time Δt2 of the internal pressure Pr isdetermined (ΔPr=P2−P1). Thereafter, this interruption routine isfinished.

FIGS. 14 and 15 show a subroutine for performing the process ofcorrecting the rotation speed of the engine 15 and the flap angle of theflaps 52 shown in the above step ST110 of FIG. 11.

Firstly, in step ST401, it is determined whether or not the initialvalue flag Fb is “0” (Fb=0). At this time, if it is determined thatFb=0, the current travel distance Lr of the lawn mower 10 is determined(step ST402). The current travel distance Lr is a value in the casewhere it is determined that the blade switch 104 is off in step ST16 ofFIG. 10. The current travel distance Pr may have any value. For example,the current travel distance Pr may be 0.

For example, in the case where the current travel speed Spr of the lawnmower 10 is constant, the control unit 117 can determine the currenttravel distance Lr by multiplying the net travel speed Spr detected bythe travel speed detection unit 112 by the travel time (accumulatedtime) of the lawn mower 10. That is, the control unit 117 has a functionof the travel distance detection unit. Further, the current traveldistance Lr can be directly detected by the travel distance detectionunit of the lawn mower 10. In the present invention, a “travel distancedetection unit 131” can determine the travel distance Lr directly and/orindirectly. That is, the lawn mower 10 has the travel distance detectionunit 131 (see FIG. 8) for detecting the travel distance Lr of the lawnmower 10.

In the next step ST403, the value of the current travel distance Lr isset to an initial value Lini of the travel distance (Lini=Lr). In thenext step ST404, the current actual weight Wr (net weight Wr) of thegrass clippings container 22 is detected by the grass clippingscontainer weight detection unit 113. In the next step ST405, the valueof the current net weight Wr is set to the initial value Wo of the netweight (Wo=Wr). In the next step ST406, the initial value flag Fb is setto “1” (Fb=1), and then, the control proceeds to the next step ST407.

In the meanwhile, in step ST401, if it is determined that the initialflag Fb is not “0” (Fb≠0), the control proceeds to step ST407 directly.

In the next step ST407, the net travel speed Spr is detected by thetravel speed detection unit 112. In the next step ST408, it isdetermined whether or not the net travel speed Spr is less thanpredetermined correction determination speed Sps (Spr<Sps). In thisregard, if it is determined that the net travel speed Spr is less thanthe correction determination speed Sps (Spr<Sps), the control proceedsto the next step ST409. In step ST409, the value of the flap angularspeed correction value θss is set to 0°, and then, the control proceedsto step ST411. That is, the flap angle θr is not corrected.

In the meanwhile, in step ST408, if it is determined that the net travelspeed Spr reaches the correction determination speed Sps (Spr≧Sps), thecontrol proceeds to the next step ST410. In step ST410, the value of theflap angular speed correction value θss is set to “−θm” (θss=−θm), andthen, the control proceeds to step ST411. θm is a predeterminedcorrection value.

Then, in step ST411, the current travel distance Lr of the lawn mower 10is determined by the travel distance detection unit 131 again. It shouldbe noted that, the above steps ST402 to ST411 are performed under acondition where the rotation speed Ner of the engine 15 and the flapangle θr of the flaps 52 are kept substantially constant.

In the next step ST412, the accumulated distance La is calculated bysubtracting the initial value Lini of the travel distance determined inthe above step ST403 from the current travel distance Lr determined instep ST411 (La=Lr−Lini). This current accumulated distance La is a valueof the accumulated distance from the time when the blade switch 104 wasturned on to the current time.

In the next step ST413, it is determined whether or not the accumulateddistance La from the time when the blade switch 104 was turned on to thecurrent time is less than the predetermined distance Ls (La<Ls). If itis determined that the accumulated distance La to the current time isless than the predetermined distance Ls (La<Ls), the control proceeds tostep ST414.

In step ST414, the rotation speed lawn condition correction value Neg ofthe engine 15 is set to “0” (Neg=0). That is, no correction is made. Inthe next step ST415, after the flap angel lawn condition correctionvalue θg of the flaps 52 is set to “0” (θg=0), the control proceeds tothe next step ST421. That is, no correction is made.

In the meanwhile, in step ST413, if it is determined that theaccumulated distance La up to the current time reaches the predetermineddistance Ls (La≧Ls), the control proceeds to step ST416. In step ST416,the current actual weight Wr (net weight Wr) of the grass clippingscontainer 22 is detected by the grass clippings container weightdetection unit 113 again.

In the next step ST417, the change amount Wa of the net weight Wr of thegrass clippings container 22, i.e., the accumulated weight Wa iscalculated by subtracting the initial value Wo of the net weight fromthe current net weight Wr of the grass clippings container 22(Wa=Wr−Wo). In this step ST417, the amount of increase in the net weightWr of the grass clippings container 22, i.e., the accumulated weight Waduring travel of the lawn mower 10 by the predetermined distance Ls canbe determined. It should be noted that, under a condition where therotation speed Ner of the engine 15 and the flap angle θr of the flaps52 are kept substantially constant, the accumulated weight Wa is a valueobtained during a period in which the lawn mower 10 travels by thepredetermined distance Ls.

In the next step ST418, it is determined whether or not the accumulatedweight Wa of the grass clippings container 22 is lighter than thepredetermined correction determination weight Ws (Wa<Ws). At this time,if it is determined that the accumulated weight Wa is below thecorrection determination weight Ws (Wa<Ws), the control proceeds to stepST421 directly.

In the above step ST418, if it is determined that the accumulated weightWa is increased to the correction determination weight Ws (Wa≧Ws), thecontrol proceeds to step ST419. In step ST419, the rotation speed lawncondition correction value Neg of the engine 15 is set to “+Nm”(Neg=+Nm). That is, a correction is made. Nm is a correction value. Inthe next step ST420, the flap angle lawn condition correction value θgof the flaps 52 is set to “+θm” (θg=+θm), and then, the control proceedsto step ST421. θm is a correction value.

In the next step ST421, the value of the target rotation speed settingvalue Nes is corrected using the rotation speed lawn conditioncorrection value Neg. Specifically, a value obtained by adding therotation speed lawn condition correction value Neg to the targetrotation speed setting value Nes is used as a new target rotation speedsetting value Nes (Nes=Nes+Neg).

In the next step ST422, the new target flap angle setting value θs ofthe flaps 52 is set, and then, the control returns to step ST110 of FIG.11. Specifically, the target flap angle setting value θs is determinedby adding the flap angular speed correction value θss and the flap anglelawn condition correction value θg to the target flap angle indicationvalue θb of the flaps 52 (θs=θb+θss+θg). The target flap angleindication value θb is a setting value which is set based on the changeamount ΔWr per fixed time Δt1 of the weight Wr and the change amount ΔPrper fixed time Δt2 of the internal pressure Pr (steps ST103, ST108, andST110).

Next, operation of each component at the time of performing the controlflow shown in FIGS. 9 to 15 will be described with reference to FIG. 16.FIG. 16 is a time chart of the lawn mower 10, showing operation of eachcomponent. In the time chart, the horizontal axis denotes time.

Now, it is assumed that the mode switch 11 is off (i.e., mulching mode),the blade switch 104 is off, the engine 15 is in the middle of rotationat the first reference rotation speed N1, and the net flap angle θr ofthe flaps 52 is zero. The grass clippings container 22 is empty.

Thereafter, when the mode switch 11 is turned on, i.e. after switchingto the bagging mode, the blade switch 104 is turned on. At this time,the rotation speed Ner of the engine 15 becomes the second referencerotation speed N2, and the net flap angle θr of the flaps 52 becomes thefirst reference flap angle θ1.

During travel of the lawn mower 10 by the predetermined distance Lsafter the blade switch 104 was turned on, in the case where the netweight Wr of the grass clippings container 22 is increased to thecorrection determination weight Ws, the rotation speed Ner of the engine15 is increased by the correction value Nm, and the flap angle θr of theflaps 52 is increased by the correction value θm.

The rotation speed Ner of the engine 15 and the flap angle θr of theflaps 52 are corrected based on the change amount Wa of the net weightWr of the grass clippings container 22 from the time when the bladeswitch 104 was turned on to the time when the lawn mower 10 traveled bythe predetermined distance Ls, i.e., based on the accumulated weight Wa.This correction continues until the blade switch 104 is turned off.

Thereafter, when the blade switch 104 is turned off, the value of thetravel distance La (accumulated distance La) of the lawn mower 10 isreset.

The above explanation is summarized as follows:

As shown in FIGS. 14 and 15, the control unit 117 implements control tokeep the rotation speed Ner of the engine 15 and the flap angle θr ofthe flaps 52 substantially constant, over an elapsed time period fromthe time of starting detection of the travel distance Lr by the traveldistance detection unit 131 until the end of the travel by thepredetermined distance Ls. Further, the control unit 117 determines thechange amount Wa of the weight Wr of the grass clippings container 22,detected by the grass clippings container weight detection unit 113until elapse of the time period. Then, the control unit 117 implementscontrol according to the change amount Wa of the weight Wr to adjust therotation speed Ner of the engine 15 and the flap angle θr of the flaps52.

In the case where the change amount Wa of the weight Wr is large, it canbe presumed that the lawn grass cut by the cutter blade 14 (grassclippings) has a lawn condition of heavy weight. In the case where thechange amount Wa of the weight Wr is small, it can be presumed that thegrass clippings have a lawn condition of light weight. In this manner,depending on the characteristics (lawn condition) of the lawn grass cutby the cutter blade 14, the rotation speed Ner of the engine 15 and theflap angle θr of the flaps 52 can be adjusted.

Thus, regardless of the lawn condition, by orienting the lawn grassgrowing on the lawn ground to stand upright by the upward air flow, itis possible to cut (clip) the lawn grass by the cutter blade 14efficiently. Further, after the lawn grass (grass clippings) cut by thecutter blade 14 is lifted upward, and swirled in the housing 11 by theupward air flow and the swirl air flow generated by the flaps 52, thelawn grass can be transported into the grass clippings container 22efficiently. Therefore, the operator can perform the lawn mowingoperation stably and highly efficiently regardless of the lawncondition. It is possible to eliminate unevenness in lawn grass afterthe lawn mowing operation due to the difference in the lawn condition,without requiring the operator to perform some operation consciously.Consequently, it is possible to improve the work efficiency of the lawnmowing operation.

Further, by adjusting the rotation speed Ner of the engine 15 and theflap angle θr of the flaps 52 depending on the characteristics (lawncondition) of the grass clippings cut by the cutter blade 14, the windamount of the transportation wind generated by the cutter blade 14 andthe flaps 52 is changed. Therefore, the grass clippings can be stored inthe grass clippings container 22 as uniformly as possible. Accordingly,it is possible to greatly improve the storage ratio of the grassclippings container 22. A larger quantity of grass clippings can bestored in the grass clippings container 22 efficiently.

Further, as shown in FIGS. 11 to 13, the control unit 117 determines thechange amount ΔWr per predetermined fixed time Δt1 of the weight Wrdetected by the grass clippings container weight detection unit 113, andthe change amount ΔPr per predetermined fixed time Δt2 of the internalpressure Pr detected by the internal pressure detection unit 111. Then,in the case where the control unit 117 determines that two conditions,i.e., the first condition where the change amount ΔWr of the weight Wris below the predetermined weight change amount reference value ΔWs andthe second condition where the change amount ΔPr of the internalpressure Pr has increased to the predetermined internal pressure changeamount reference value ΔPs, are satisfied, the control unit 117 controlsthe actuator 60 in a manner that the flaps 52 are placed in asubstantially horizontal state.

In the case where the change amount ΔWr of the weight Wr of the grassclippings container 22 is small, and the change amount ΔPr of theinternal pressure Pr of the housing 11 is large, the following twopresumptions can be made.

The first presumption is made in the case where the change amount ΔWr ofthe weight Wr of the grass clippings container 22 is “small”. In thiscase, the grass clippings container 22 stores a substantial amount ofgrass clippings to almost reach the storage capacity limit. If thechange amount ΔPr of the internal pressure Pr of the housing 11 is“large”, the transportation window does not flow from the housing 11toward the grass clippings container 22 smoothly. Therefore, in the casewhere the change amount ΔWr of the weight Wr of the grass clippingscontainer 22 is small and the change amount ΔPr of the internal pressurePr of the housing 11 is large, it can be presumed that the grassclippings container 22 has almost reached its storage capacity limit,and for this reason, the transportation wind does not flow from thehousing 11 to the grass clippings container 22 smoothly.

The second presumption is made in the case where the change amount ΔWrof the weight Wr of the grass clippings container 22 is small and thechange amount ΔPr of the internal pressure Pr of the housing 11 islarge. In this case, it is presumed that jamming of the grass clippingshas occurred in the grass clippings discharge passage 21 between thehousing 11 and the grass clippings container 22.

The control unit 117 can accurately determine that the grass clippingscontainer 22 has almost reached its storage capacity limit, or jammingof the grass clippings has occurred in the grass clippings dischargepassage 21 between the housing 11 and the grass clippings container 22,based on the change amount ΔWr of the weight Wr of the grass clippingscontainer 22 and the change amount ΔPr of the internal pressure Pr ofthe housing 11.

When the grass clippings container 22 has almost reached its storagecapacity limit, or when jamming of the grass clippings has occurred inthe grass clippings discharge passage 21 between the housing 11 and thegrass clippings container 22, the control unit 117 place the flaps 52 ina substantial horizontal state. As a result, the quantity of the wind ofthe upward air flow and the swirl air flow generated by the flaps 52,the swirl flow of the air, and the transportation wind is decreased.Therefore, the grass clippings do not flow from the housing 11 to thegrass clippings container 22 very much. Consequently, jamming of thegrass clippings does not occur easily between the housing 11 and thecutter blade 14. That is, before jamming of the grass clippings occursbetween the housing 11 and the cutter blade 14, the flaps 52 can beplaced in the substantially horizontal state. It is possible to preventphenomenon where the rotating cutter blade 14 collides with the grassclippings. Therefore, it is possible to improve the durability of theentire lawn mower 10 and the drive source 15.

Further, as shown in FIG. 11, if the control unit 117 determines thatthe two conditions (the first condition and the second condition) aresatisfied, the control unit 117 implements control to drive the alarm119.

In this manner, it is possible to notify the operator by the alarm 119that the grass clippings container 22 has almost reached its storagecapacity limit, or jamming of the grass clippings has occurred in thegrass clippings discharge passage 21 between the hosing 11 and the grassclippings container 22. The operator can learn the storage capacitylimit of the grass clippings container 22 and the jamming state of thegrass clippings promptly.

Further, as shown in FIG. 11, the control unit 117 implements control ofat least one of the rotation speed Ner of the engine 15 and the flapangle θr of the flaps 52 in accordance with the weight Wr detected bythe grass clippings container weight detection unit 113.

When the grass clippings container 22 is light, the grass clippingscontainer 22 has the extra storage capacity to store the grass clippingsmuch more. In this case, the control unit 117 reduces the rotation speedNer of the drive source 15 or reduces the flap angle θr of the flaps 52toward the horizontal side, or implements both of these controls.Consequently, the wind amount of the transportation wind generated bythe cutter blade 14 and the flaps 52 becomes small. The grass clippingscut by the cutter blade 14 can be transported from the housing 11 to thegrass clippings container 22, and it is possible to store the grassclippings at a position near the inlet of this grass clippings container22.

When the grass clippings container 22 is heavy, the grass clippingscontainer 22 does not have the extra storage capacity to store the grassclippings much more. In this case, the control unit 117 changes therotation speed Ner of the drive source 15, or increases the flap angleθr of the flaps 52, or implement both of these controls. Consequently,the wind amount of the transportation wind generated by the cutter blade14 and the flaps 52 becomes large. It is possible to transport the grassclippings from the housing 11 to the grass clippings container 22, andstore the grass clippings at a deeper position in the grass clippingscontainer 22.

As descried above, by controlling at least one of the rotation speed Nerof the drive source 15 and the flap angle θr of the flaps 52 incorrespondence with the weight Wr detected by the grass clippingscontainer weight detection unit 113, it is possible to store the grassclippings in the grass clippings container 22 as uniformly as possible.Therefore, it is possible to greatly improve the storage ratio of thegrass clippings container 22. It is possible to efficiently store thelarger quantity of grass clippings in the grass clippings container 22.The frequency of replacing the grass clippings container 22 can bereduced, and improvement in the efficiency of the lawn mowing operationis achieved. Further, it is not required for the operator to performsome operation consciously to increase the storage ratio of the grassclippings container 22.

Further, as shown in FIG. 9, the control unit 117 implements control ofthe bagging mode and the control of the mulching mode in accordance withthe switch signals received from the mode switch detection unit 114.Therefore, the operation of the lawn mower 10 can be performed in anoperation mode arbitrarily selected between the bagging mode and themulching mode.

Further, as shown in FIGS. 9, 11, and 15, when the control unit 117receives a signal of the bagging mode from the mode switch detectionunit 114 (including the operation switch), the control unit 117implements control in a manner that the rotation speed Ner of the drivesource 15 is changed to the predetermined reference rotation speed Nes(target rotation speed setting value Nes) and the flap angle θr of theflaps 52 is changed to the predetermined reference flap angle θs (targetflap angle setting value θs).

Therefore, for example, by selecting the bagging mode beforehand, priorto starting the lawn mowing operation, at least one of the rotationspeed Ner of the drive source 15 and the flap angle θr of the flaps 52can be placed in a suitable state before starting operation.Accordingly, further improvement in the work efficiency of the operationis achieved.

The lawn mower 10 of the present invention is suitably adopted as awalk-behind lawn mower.

While the invention has been particularly shown and described withreference to a preferred embodiment, it will be understood thatvariations and modifications can be effected thereto by those skilled inthe art without departing from the scope of the invention as defined bythe appended claims.

What is claimed is:
 1. A lawn mower comprising: a cutter blade rotatableabout a rotation shaft extending in a vertical direction; a drive sourceconfigured to drive the cutter blade through the rotation shaft; and agrass clippings container configured to store lawn grass cut by thecutter blade and transported by transportation wind generated by thecutter blade, a flap provided for the cutter blade, the flap having aflap angle changeable along a horizontal line which is perpendicular tothe rotation shaft; an actuator configured to control the flap angle ofthe flap; a control unit configured to control the actuator; a grassclippings container weight detection unit configured to detect weight ofthe grass clippings container; and a travel distance detection unitconfigured to detect travel distance of the lawn mower, wherein thecontrol unit is configured to: implement control in a manner thatrotation speed of the drive source and the flap angle of the flap arekept substantially constant over an elapsed time period from time whendetection of the travel distance is started by the travel distancedetection unit to time when travel of predetermined distance iscompleted; determine a change amount of the weight of the grassclippings container detected by the grass clippings container weightdetection unit over the elapsed time period; and implement control in amanner that the rotation speed of the drive source and the flap angle ofthe flap are adjusted in accordance with the change amount of theweight.